1. Field of the Invention
The present invention relates to a method for manufacturing a liquid ejecting head used with a liquid ejecting system for ejecting liquid from a liquid discharge nozzle as a liquid droplet.
2. Related Background Art
A liquid ejecting head used with a liquid ejecting system (ink jet system) includes a plurality of liquid discharge nozzles for discharging liquid such as ink, liquid supply paths communicated with the respective liquid discharge nozzles, and discharge energy generating elements (for example, electrical/thermal converting elements) associated with the respective liquid discharge nozzles so that, by applying a drive signal corresponding to discharge information to the discharge energy generating element to afford discharge energy to liquid within the liquid discharge nozzle associated with the discharge energy generating element, the liquid is discharged from a minute discharge port of the liquid discharge nozzle as a flying liquid droplet, thereby effecting the recording.
As liquid discharge heads of this kind and nozzle members therefor, various techniques have been proposed, and various manufacturing method therefor have also been proposed. Now, an example of the conventional liquid discharge head and nozzle member therefor will be described with reference to FIGS. 11 and 12. FIG. 11 is a view showing a liquid discharge head and a nozzle member disclosed in Japanese Patent Application Laid-open No. 6-31918 (1994), for example, wherein a nozzle member 101 is formed from a silicon wafer cut and polished to have a surface having a crystal <100> face. The nozzle member includes a through opening 102 for supplying liquid and liquid discharge nozzles 103. A heater board (element substrate) 105 comprises silicon chips on which plural electrical/thermal converting elements (referred to as “heaters” hereinafter) 106 as discharge energy generating elements are provided. The nozzle member 101 and the heater board 105 are joined or adhered to each other so that the nozzles 103 are opposed to the heaters 106, and thin or fine nozzles each having a triangular cross-section are defined between the nozzle member 101 and the heater board 105, and the heaters 106 are included in the respective nozzles 103.
The nozzle member 101 is manufactured as follows. That is to say, an inorganic film made of SiO2 is formed on the surface of the silicon wafer constituting the nozzle member 101 by a film forming method such as thermal oxidation or CVD, and a resist material of an organic film is formed on the nozzle surface by a spin-coat method. Then, patterning corresponding to shapes of the nozzles 103 and the through opening 102 is effected, and, thereafter, anisotropical wet etching is effected while immersing the nozzle member 101 into etching liquid such as KOH or TMAH. As a result, the etching grows along a <111> face of the silicon, and, when a silicon wafer having a surface of a <100> face is used, since the <111> face is inclined by 54.7 degrees with respect to the surface, the nozzles 103 and the through opening 102 are formed in shapes as shown in FIGS. 11 and 12.
When the liquid ejecting head is formed by joining or adhering the nozzle member 101 formed in this way to the heater board 105, since there remains a wall portion 110 between the nozzles 103 and the through opening 102 in the nozzle member 101, flow paths for liquid cannot be reserved. To reserve such flow paths, as shown in FIG. 12, f/low path walls 107 are formed on the heater board 105 by patterning polyimide material, thereby reserving liquid supply paths as shown by the arrow 108.
In the liquid ejecting head shown in FIGS. 11 and 12, liquid such as ink is supplied from a liquid tank (not shown) and is directed into the through opening 102 as a liquid supply path and reaches the nozzles 103 through the aforementioned liquid supply paths. The plurality of heaters 106 provided on the heater board 105 are controlled by a control circuit (not shown) so that the heaters 106 are selectively energized in response to recording information. A heater 106 energized in response to the recording information generates heat to heat the liquid within the corresponding nozzle 103, and the heated liquid is boiled when it exceeds a certain critical temperature, thereby forming a bubble. Due to an increase in volume caused by the formation of the bubble, a part of the liquid is forcibly pushed out from the nozzle 103 to fly onto a recording medium such as paper. By repeating such operations, a recorded image is completed.
In the above-mentioned conventional technique, by using the silicon wafer having a surface of a <100> face as the nozzle member, although there are provided advantages that the depth can be adjusted by the configuration of the patterning since the etching grows obliquely, and that the nozzles and the through opening can be formed by a single etching, as shown in FIG. 12, since the wall portion 110 remains between the nozzles 103 and the through opening 102, flow path walls 107 must be formed on the heater board 105 by patterning a polyimide material to reserve the liquid supply paths shown by the arrow 108 in FIG. 12, which makes the manufacturing processes of the heater board complicated.
Further, since the shape of each nozzle 103 has a triangular cross-section, as shown in FIG. 11, the wall thickness between adjacent nozzles 103 is increased, which worsens efficiency for forming the nozzles and works against a high density arrangement of nozzles.
Furthermore, in the liquid ejecting head in which heaters are used as the discharge energy generating elements, to solve a problem that the force of the bubble for discharging the liquid escapes through the through opening 102, as shown in FIG. 13, there has been proposed a method in which a valve 109 is provided above each heater 106 to enhance the liquid discharging efficiency. That is to say, the valve 109 serves to be moved upwardly by the bubble force when the bubble is generated by the heating of the heater 106 and to prevent the bubble from escaping toward the through opening 102. However, in the case there a nozzle 103 has a triangular cross-section, when the valve 109 is moved upwardly, the valve is apt to contact the walls of the nozzle 103, and, in order to prevent the valve 109 from contacting the walls of the nozzle, the nozzle width must be increased excessively, which works against a high density arrangement of nozzles.
Further, there have also been proposed methods for forming nozzles by working material other than silicon, and, according to such methods, although there is provided an advantage that the nozzles can be formed as free configurations by using resin and the like, when the number of nozzles is increased to lengthen the recording head, due to the difference in thermal expansion rates between the nozzle member and the heater board, good adhesion between the nozzle member and the heater board cannot be achieved, which leads to limitation of the length of the liquid ejecting head.